title: Highly dynamic motion of crown ethers along oligolysine peptide chains.
abstract: Molecular mobility has attracted considerable attention in supramolecular chemistry and biochemistry, but the simple question of whether a small molecule can move directly between different binding sites of a multitopic host without intermediate dissociation has not been addressed so far. To study such processes, we consider hydrogen/deuterium exchange experiments on a model system comprising complexes formed between 18-crown-6 and oligolysine peptides. Because direct binding-site hopping is indistinguishable in solution from a dissociation/reassociation mechanism, here we show that the high vacuum of a mass spectrometer offers a unique environment for probing such processes. The highly dynamic motion of crown ethers along oligolysine peptide chains proceeds mechanistically by a simultaneous transfer of the crown ether from its ammonium ion binding site to a nearby amino group together with a proton. Furthermore, the exchange experiments unambiguously reveal the zwitterionic structure of the 18-crown-6/oligolysine complexes, highlighting the versatility and potential of gas-phase experiments for investigating non-covalent interactions.
authors.affiliation: Institut für Chemie und Biochemie der Freien Universität, Berlin, Germany.
authors.forename: Dominik P
authors.initials: DP
authors.lastname: Weimann
authors.forename: Henrik D F
authors.initials: HD
authors.lastname: Winkler
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Falenski
authors.forename: Beate
authors.initials: B
authors.lastname: Koksch
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Schalley
mesh_terms: D001665:Binding Sites; D043844:Crown Ethers / Q000737:chemistry*; D041961:Deuterium Exchange Measurement; D008239:Lysine / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry*; D009038:Motion; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry
chemical_list: D043844:Crown Ethers; D009842:Oligopeptides; D000644:Quaternary Ammonium Compounds; D008239:Lysine